1. Field of the Invention
The present invention relates to a vehicular headlamp having therein a projector-type lamp unit.
2. Prior Art
In a conventionally known vehicular headlamp, a predetermined light distribution pattern is formed by light radiation from a projector-type lamp unit; and this projector-type lamp unit typically includes a projection lens disposed on the optical axis of the lamp that extends in the longitudinal direction of a vehicle, a light source bulb provided behind a rear focal point of the projection lens, and a reflector which condenses and reflects light from the light source bulb toward the optical axis in a forward direction.
Japanese Utility Model Application Publication (Kokoku) No. H2-47704 discloses a vehicular headlamp of this type; and in this headlamp, the light source bulb is fixedly inserted (that is, inserted and fixed) in the reflector from a location that is on one side of the optical axis.
A typical projector-type lamp unit is long in the longitudinal direction due to its structure. Therefore, in a vehicular headlamp that has such a projector-type lamp unit, it is necessary that the lamp body have a sufficient depth dimension in order to ensure accommodation space for the projector-type unit.
For this reason, in the above Japanese Utility Model Application Publication (Kokoku) No. H2-47704, since the light source bulb is fixedly inserted in the reflector from the side of the optical axis, the rearward-projecting amount of the lamp unit is small and its longitudinal length is reduced as well.
However, in this projector-type lamp unit the light source bulb is fixedly inserted in the reflector from the side of the optical axis or from a position that is on a horizontal plane at the same horizontal level as the optical axis, the lamp having such a lamp unit has problems.
In a projector-type lamp unit, the side area, with respect to the optical axis, of the reflecting surface of the reflector is most suitably used for forming a diffusion area of a light distribution pattern. However, if the light source bulb is fixedly inserted in the reflector on the same horizontal plane as the optical axis, the hole for inserting the light source bulb is formed in such side area of the reflecting surface, and as a result, the side area of the optical axis cannot be effectively used for controlling the distribution light. Accordingly, it is difficult to ensure sufficient brightness of the diffusion area of the light distribution pattern.